FLOWERING AND AIRBORNE POLLEN – A NOVEL STATISTICAL APPROACH

The time pattern of fl owering signifi cantly affects the pollen season, its beginning, length and the concentration of pollen grains in air. The forecasting models used in aerobiological studies were chiefl y based on the elements of weather conditions; however, recently the phenology of pollen shedding has been taken into consideration in these models more and more frequently. The aim of the presented investigations was to determine to what extent the fl owering and the occurrence of allergenic pollen grains in air coincided in time. The investigation was carried out in Rzeszow (SE Poland) in the years 2003-2004. The fl owering of 19 allergenic plant species was observed and seven phenophases were distinguished. Aerobiological monitoring was based on the volumetric method. In the case of most herbaceous plants, the fl owering period overlapped the pollen season, high concentrations of pollen being recorded throughout several phenophases. In general, the pollen of trees occurred during very short periods, frequently during one phenophase, while the investigated phenomena were missing each other. The most intensive growth of infl orescences of alder, hazel and birch was observed at the beginning of full fl owering or towards the end of full fl owering.


INTRODUCTION
The annual life cycle of plants can be divided into many successive or parallel developmental stages called phenophases.Classic phenological observations associated with modern research techniques (e.g., remote sensing, chemical analyses) offer perfect sensitive methods in monitoring environmental changes (S t ud e r et al. 2007).The results of such studies are widely used in numerous fi elds of science (ecology, biometeorology) and also implemented in the practice of agriculture, tourism, forestry, and medicine.The studies on fl owering phenology help in the interpretation of results of aerobiological investigations and also in a more and more precise elaboration of forecasting models of aerobiological processes.It is particularly important in fore- In Poland, K a s p r z y k (2003) was the fi rst to compare the fl owering and the occurrence of pollen of selected allergenic plant species.In the work presented here, these investigations have been continued.The basic aim of the work was to ascertain how far the fl owering and the occurrence of pollen in air of chosen plant species -important for sensitized people -were overlapping in time.

MATERIALS AND METHODS
The investigations were carried out in Rzeszów, southeastern Poland, in 2003 and 2004.Aerobiological monitoring was based on the volumetric method using a Hirsttype pollen trap (Lanzoni VPPS 2000) set 12 m above the ground level.The phenological observations were carried out each year from 1 st of January to the end of fl owering of the last of the investigated species.The Ł u k a s z e w i c z (1968) method was used to record the successive 7 phenophases (F) of the generative development of plants: F1 -the appearance of the fi rst fl ower or infl orescence buds; F2 -blossoming of the fi rst fl owers; F3 -beginning of full fl owering (25% of fl owers open); F4 -the fi rst fl owers shedding blossom; F5 -end of full blossoming (75% of fl owers shedding blossom); F6 -the last fl ower buds; F7 -end of blossoming (from the day of the last fl owers ending blooming to the end of the year).
The crucial point of the work was to compare the pattern of occurrence of plant pollen in air with the pattern of fl owering.For each distinguished phenophase, the respective total of pollen grains and the average daily number of grains in the phase were calculated.A further step included the calculation of the weighted mean of the phase number and of the weighted variance.The statistical weight of the given phase was the mean number of grains per diem in this phase.Thus, the mean shows in which phase on average pollen occurs in air, while the variance shows the occurrence of pollen in air in one phase (low variance) or the distribution of this process in many phases (high variance).With the aim of evaluating the accordance of the time of fl owering periods, the synchronization index (X) was calculated according to the formula proposed by O l l e r t o n and L a c k (1998).When this index is close to one, it indicates a high level of fl owering synchronization.The phenological studies were expanded to include measurements of length of male infl orescences in three selected tree species: C. avellana, A.glutinosa and B. pendula.The length of selected infl orescences was measured at intervals of a few days in the whole period of fl owering.The obtained data were used in calculating the rate of infl orescence growth in an appointed time unit (length increase/period).

RESULTS
The comparison of the pattern of fl owering in the observed plants with the occurrence of pollen grains in air allows distinguishing three groups.In the fi rst group, the period of the greatest number of pollen grains corresponded with phenophases 1-2.9 on average, i.e. pollen chiefl y occurred in air before the start of fl owering in the observed individuals.Such a dependence characterized F. excelsior, C. betulus, J. regia and Q. robur.In the case of most plant species observed, the highest numbers of their pollen were noted during intensive fl owering (the average phase 3-4.9).This group includes most grasses, both species of sorrel, small plantain, and some tree species, e.g. A. incana.The third group includes species whose pollen was found in air after the period of intensive fl owering of individuals.This pattern of the investigated phenomena concerned C. avellana, S. fragilis and A. pratensis.In a few cases, only the course of the investigated phenomena differed in the years (A. glutinosa, B. pendula, A. odoratum and D. glomerata).
The value of variance was taken into consideration as a measure of dispersion of pollen among the phenophases and was used in arranging species according to this variance (Fig. 1).The order is not exactly the same in 2003 and 2004; nonetheless, the groups of species attaining very high or very low values of variance are similar in both years.Two groups of species were distinguished.In the fi rst group, there are species whose pollen chiefl y appeared in one phenophase and the value of variance is low: s 2 <0.5.In general, such a situation was found in the case of trees.In the species of the second group, pollen grains occurred at high concentrations throughout several phenophases and the variance was high: s 2 >1.This situation concerned most herbaceous plants (R. acetosa, R. acetosella, P. lanceolata, D. glomerata, P. pratensis, A. pratensis, P. pretense; Fig. 1).
The periods of fl owering of observed individuals were compared between the sites of the investigation.The similarities were very high, as was confi rmed by high numerical values of synchronization indices (average value X=0.8).No signifi cant differences were found in the values of these indices depending on the seasons of the year, years, or taxon.
The rates of length increase in infl orescences of A. gutinosa, C. avellana, and B. pendula were not uniform in the investigated period.A repeated increase in the growth rate was observed towards the end of fl owering, as illustrated by matching curves of the degree fi ve polynomial (e.g., A. glutinosa 2004).In the case of B. pendula, in 2004 the exponentiation function ignores this effect (Fig. 2).

DISCUSSION
The association of the occurrence of pollen in air and the pattern of fl owering is obvious, but not always direct.This is confi rmed by the literature (L a t t o r e , 1999; J a t o et al. 2002; K a s p r z y k , 2003; E s t r e ll a et al. 2006; S t a c h et al. 2006) and the presented results.Differences between these phenomena result both from their specifi city and the research methods.Depending on how the pollen trap was placed, the content of pollen in air did not only concern the town but also the region.In general, the pollen season is longer than  Kwitnienie a występowanie pyłku w powietrzu -nowe statystyczne podejście do problemu

Fig. 1 .
Fig. 1.Species grouped into the low and high-variance class, and then ordered according to the mean phase.
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Idalia Kasprzyk 1 , Adam Walanus 2 1
Department of Environmental Biology, University of Rzeszów, Rejtana 16c, 35-959 Rzeszów, Poland; e-mail: idalia@univ rzeszow.pl 2 Department of Geoinformatics, AGH University of Science and Technology, Al.Mickiewicza 30, 30-059 Crakow, Poland casting the concentrations of allergenic pollen or yields of economically important crops (P h e n o l o g y ….., 2003; O r l a n d i et al. 2005; G a l a n , 2007).In aerobiological studies the forecasting models were chiefl y based on climate and the pattern of weather conditions (O r l a n d i et al. 2005).In recent years attempts, have been made to include the biotic factor, i.e. the fl owering, in these models.The results show that, depending on the geobotanical character of the investigated region and its climate, the taxonomical level of a given taxon, the location and sources of pollen, these phenomena are more or less connected with each other (J a t o et al. 2002; E s t r e l l a et al. 2006; S t a c h et al. 2006).